Semiconductor devices are used in many electronic and other applications. Semiconductor devices comprise integrated circuits that are formed on semiconductor wafers by depositing many types of thin films of material over the semiconductor wafers, and patterning the thin films of material to form the integrated circuits.
There is a demand in semiconductor device technology to integrate many different functions on a single chip, e.g., manufacturing analog and digital circuitry on the same die. In such applications, large capacitors are extensively used for storing an electric charge. They are rather large in size, being several hundred micrometers wide depending on the capacitance, which is much larger than a transistor or memory cell. Consequently, such large capacitors occupy valuable silicon area, increasing product cost. Such large capacitors are typically used as decoupling capacitors for microprocessor units (MPU's), RF capacitors in high frequency circuits, and filter and analog capacitors in mixed-signal products. Key attributes of MIM capacitors are high linearity over broad voltage ranges (low voltage coefficients), low series resistance, good matching properties, small temperature coefficients of capacitance, low leakage currents, high breakdown voltage and sufficient dielectric reliability.
For economic reasons, a large number of parasitic MIM capacitors are built in the back end of the line process during metallization. As these are parasitic capacitors, they share a common process flow with the baseline processes. Consequently, these capacitors are disposed in low-k dielectric layers as low-k dielectrics are used above active devices to minimize interconnect parasitic capacitance. However, introduction of low-k materials introduces a number of challenges for the design of MIM capacitors. For example, the capacitance of the MIM capacitors may change due to drift in dielectric constant of the dielectrics, the dielectric constant drifting either with temperature or applied stress (voltage). However, a number of applications require precision MIM capacitors immune from environmental or operating variability.
Thus, what are needed in the art are MIM capacitors that are immune from environmental and/or operating conditions, and fabricated at a minimal cost.